Polishing slurries and methods for chemical mechanical polishing

ABSTRACT

Aqueous polishing slurries for chemical-mechanical polishing are effective for polishing copper at high polish rates. The aqueous slurries according to the present invention may include soluble salts of molybdenum dissolved in an oxidizing agent and molybdic acid dissolved in an oxidizing agent. Methods for polishing copper by chemical-mechanical planarization include polishing copper with low pressures using a polishing pad and a aqueous slurries including soluble salts of molybdenum dissolved in an oxidizing agent and molybdic acid dissolved in an oxidizing agent, particles of MoO 3  dissolved in an oxidizing agent, and particles of MoO 2  dissolved in an oxidizing agent.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of co-pending U.S. patent applicationSer. No. 10/846,718, filed on Jun. 13, 2004, which is acontinuation-in-part of co-pending U.S. patent application Ser. No.10/631,698, filed on Jul. 30, 2003, which are hereby incorporated byreference for all that they disclose.

TECHNICAL FIELD

This invention relates to chemical-mechanical planarization processes ingeneral and more specifically to slurries and methods forchemical-mechanical planarization.

BACKGROUND

Chemical-mechanical polishing (CMP) is the term used to refer to aprocess that is used in semiconductor manufacture. As its name implies,the CMP process is typically used in semiconductor processing to polish(e.g., planarize) the surface of the semiconductor wafer. The CMPprocess is relatively new in that, until recently, conventionalprocesses were sufficient with the comparatively low circuit densitiesinvolved. However, increases in circuit densities (e.g., the transitionfrom wafers having 0.25 micron features to 0.18 micron features, andeven to 0.045 micron features) have forced the need to develop newprocesses for planarizing the wafer, of which CMP has become favored.Similarly, the more recent shift away from aluminum interconnecttechnology to copper interconnect technology has further favored the useof CMP to polish (e.g., planarize) semiconductor wafers.

Briefly, the chemical-mechanical polishing (CMP) process involvesscrubbing a semiconductor wafer with a pad in the presence of achemically reactive slurry that contains abrasive particles. As its nameimplies, the polishing action of the chemical-mechanical polishing (CMP)process is both chemical and mechanical. Chemicals aid in materialremoval by modifying the surface film while abrasion between the surfaceparticles, pad, and the modified film facilitates mechanical removal. Itis believed that this synergistic interplay between the chemical andmechanical components in the process is the key to effective polishingof the CMP process.

While the CMP process is being increasingly used in semiconductormanufacturing processes, the CMP process remains poorly understood, andthe exact mechanisms though which the process works have not beendetermined. For example, while certain parameters for the CMP processhave been developed that are satisfactory for wafers utilizing aluminuminterconnect technology, those same process parameters have not provento be particularly satisfactory for use with wafers utilizing copperinterconnect technology. One important requirement of a successful CMPslurry for copper is a high polish rate. High polish rates lead toshorter copper overburden polishing times.

SUMMARY OF THE INVENTION

The following summary is provided as a brief overview of the claimedproduct and process. It shall not limit the invention in any respect,with a detailed and fully-enabling disclosure being set forth in theDetailed Description of Preferred Embodiments section. Likewise, theinvention shall not be restricted to any numerical parameters,processing equipment, chemical reagents, operational conditions, andother variables unless otherwise stated herein.

The claimed invention involves novel aqueous slurries which exhibit highpolish rates for copper when used in the CMP process at low pressures.One embodiment of aqueous slurries according to the present inventioncomprises soluble salts of molybdenum dissolved in deionized water andan oxidizing agent.

Embodiments of aqueous slurries may contain dissolved soluble salts ofmolybdenum in amounts ranging from about 0.1% to about 10% by weight ofthe soluble salts of molybdenum and the oxidizing agent may comprise anyone or a mixture of hydrogen peroxide (H₂O₂), ferric nitrate (Fe(NO₃)₃),potassium iodate (KIO₃), nitric acid (HNO₃), potassium permanganate(KMnO₄), potassium persulfate (K₂S₂O₈), ammonium persulfate((NH₄)₂S₂O₈), potassium periodate (KIO₄), and hydroxylamine (NH₂OH).Additionally, complexing agents may be used in the molybdenum trioxide(MoO₃) aqueous slurry. Complexing agents may comprise any one or amixture of glycine (C₂H₅NO₂), alanine (C₃H₇NO₂), amino butyric acids(C₄H₉NO₂) ethylene diamine (C₂H₈N₂), ethylene diamine tetra acetic acid(EDTA), ammonia (NH₃), family of mono, di, and tri-carboxylic acids likecitric acid (C₆H₈O₇), phthalic acid (C₆H₄(COOH)₂), oxalic acid (C₂H₂O₄),acetic acid (C₂H₄O₂), succinic acid (C₄H₆O₄), and family of aminobenzoic acids.

Embodiments of slurries containing the soluble salts of molybdenum mayalso be provided with a nonionic surfactant, an anionic surfactant, or acationic surfactant. The anionic surfactant in the aqueous slurry maycomprise any one or a mixture of polyacrylic acid (PAA), a carboxylicacid or its salt, a sulfuric ester or its salt, a sulfonic acid or itssalt, a phosphoric acid or its salt, and a sulfosuccinic acid or itssalt. The cationic surfactant in the aqueous slurry may comprise any oneor a mixture of a primary amine or its salt, a secondary amine or itssalt, a tertiary amine or its salt, and a quaternary amine or its salt.The nonionic surfactant may comprise any one or a mixture of one of manypolyethylene glycols.

Still yet other embodiments of aqueous slurries may be provided with acopper corrosion inhibitor which may comprise any one or a mixture ofheterocyclic organic compounds including benzotriazole (BTA),benzimidazole, poly triazole, phenyl triazole, thion and theirderivatives. Further embodiments of slurries may contain any combinationof these surfactants and corrosion inhibitors.

The oxidizing agents may oxidize the copper as well as react withmolybdate ions present in the slurry. The new per-molybdate orperoxy-molybdate ions are expected to further oxidize and complex withcopper, thereby providing high polish rates. Similar high polishingaction may also occur by use of tungstates, vanadates, chromates andsimilar transition metal oxide ions or peroxy ions with or without themolybdate ions.

Aqueous slurries may optionally include acids or bases for adjusting thepH within an effective range from about 1 to about 14. Yet additionalembodiments of slurries according to the invention may also be providedwith supplemental ceramic/metal oxide particles. The supplementalceramic/metal oxide particles may be added as colloidal particles or asfumed Aerosil® particles. Such supplemental ceramic/metal oxideparticles used in the aqueous slurry may comprise any one or a mixtureof silica, ceria, aluminia, zirconia, titania, magnesia, iron oxide, tinoxide, and germania.

The present invention also includes a novel method of planarizing copperby chemical-mechanical planarization. The method of the presentinvention comprises providing an aqueous slurry comprising dissolvedsoluble salts of molybdenum in deionized water and an oxidizing agent.The method further comprises polishing copper with the aqueous slurryusing a polishing pad and pressures in a range of about 0.5 psi to about6.0 psi, and more preferably between about 0.5 psi and about 2.0 psi.

The present invention also includes another novel method of planarizingcopper. The method of the present invention comprises providing anaqueous slurry comprising dissolved MoO₃ and an oxidizing agent. Themethod further comprises polishing copper with the aqueous slurry usinga polishing pad at pressures between about 0.5 psi and about 6.0 psi,and more preferably between about 0.5 psi and about 2.0 psi.

The present invention also includes yet another novel method ofplanarizing copper by chemical-mechanical planarization. The method ofthe present invention comprises providing an aqueous slurry comprisingdissolved MoO₂ and an oxidizing agent and polishing copper with theaqueous slurry using a polishing pad at pressures between about 0.5 psiand about 6.0 psi, and more preferably between about 0.5 psi and about2.0 psi.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Broadly described, embodiments of aqueous slurries according to thepresent invention may comprise a molybdenum oxide (MoO₂) polishingmaterial and an oxidizing agent. The MoO₂ polishing material may bepresent in an amount of about 0.5 to about 10 wt. %, such as about 1 toabout 3 wt. %, and more preferably in an amount of about 3 wt. %. Themolybdenum oxide polishing material may comprise fine particles of MoO₂having a mean particle size in the range of about 25 nanometers (nm) toabout 1 micron, such as about 25 nanometers to about 560 nm, and morepreferably about 50 to 200 nm, as measured by a Horiba laser scatteringanalyzer.

The MoO₂ particles may be produced from a variety ofmolybdenum-containing precursor materials, such as, for example,ammonium molybdates and related compounds, as well as molybdenum oxidesprepared from a variety of processes known in the art, whereinmolybdenum precursors and products can be made into particles within thesize ranges specified herein. Alternatively particles of MoO₂ may bereduced in size to the ranges specified herein by any of a variety ofmilling methods known in the art, such as attrition milling assisted bythe use of appropriate reagents.

By way of example, embodiments of slurries according to the presentinvention may utilize particles of MoO₂ produced from a precursormaterial comprising nano-particles of MoO₃. Nano-particles of MoO₃ arecommercially available from the Climax Molybdenum Company of Ft.Madison, Iowa (US). Alternatively, nano-particles of MoO₃ may beproduced in accordance with the teachings provided in U.S. Pat. No.6,468,497 B1, entitled “Method for Producing Nano-Particles ofMolybdenum Oxide,” which is hereby incorporated herein by reference forall that it discloses.

Regardless of whether the nano-particles of MoO₃ are obtainedcommercially or manufactured in accordance with the teachings providedin U.S. Pat. No. 6,468,497 B1, identified above, the MoO₂ particlescomprising the polishing material may be produced by heatingnano-particles of MoO₃ for a time sufficient to convert substantiallyall of the MoO₃ to MoO₂. More specifically, the nano-particles of MoO₃may be heated in a reducing atmosphere (e.g., hydrogen) to a temperaturein the range of about 400 C to about 700 C (550 C preferred). Times maybe in the range of about 30 to about 180 minutes, as may be required toreduce MoO₃ to MoO₂ in sufficient quantities. Heating may beaccomplished in a rotary furnace, although other types of furnaces maybe used. If necessary, the resulting MoO₂ product may then be ground toproduce an MoO₂ polishing material having a mean particle diameterwithin the ranges specified herein. A particle classification step mayoptionally be used to ensure that the resulting MoO₂ polishing materiallacks particles that may cause damage during polishing.

The oxidizing agent may comprise any one or a mixture of ferric nitrate(Fe(NO₃)₃), nitric acid (HNO₃), potassium iodide (KI), and potassiumiodate (KIO₃). Ferric nitrate oxidizing agent may be present inconcentrations ranging from about 0.05 to about 0.2 molar (M) Fe(NO₃)₃,such as about 0.1 to about 0.2M Fe(NO₃)₃, and more preferably in aconcentration of about 0.2 M Fe(NO₃)₃. Nitric acid oxidizing agent maybe present in amounts ranging from about 0.5 to about 2 wt. % HNO₃, suchas about 1 to about 2 wt. % HNO₃, and more preferably in an amount ofabout 2 wt. % HNO₃. Potassium iodide oxidizing agent may be present inamounts ranging from about 0.5 to about 5 wt. % KI, such as about 1 toabout 5 wt. % KI, and more preferably in an amount of about 3 wt. % KI.Potassium iodate oxidizing agent may be present in amounts ranging fromabout 1 to about 5 wt. % KIO₃, such as about 1 to about 3 wt. % KIO₃,and more preferably in an amount of about 3 wt. % KIO₃.

Additional oxidizing agents may comprise any one or a mixture ofhydroxylamine hydrochloride ((NH₂OH)Cl) and potassium permanganate(KMnO₄). Hydroxylamine hydrochloride oxidizing agent may be present inamounts ranging from about 1 to about 5 wt. % (NH₂OH)Cl, such as about 2to about 4 wt. % (NH₂OH)Cl, and more preferably in an amount of about 3wt. % (NH₂OH)Cl. Potassium permanganate oxidizing agent may be presentin amounts ranging from about 1 to about 5 wt. % KMnO₄, such as about 2to about 4 wt. % KMnO₄, and more preferably in an amount of about 3 wt.% KMnO₄. However, the polishing rates with slurries containinghydroxylamine hydrochloride and potassium permanganate are generallylower than with the other oxidizing agents identified herein.

Embodiments of slurries according to the present invention may also beprovided with an anionic surfactant or a cationic surfactant. Theanionic surfactant used in the aqueous slurry may comprise any one or amixture of polyacrylic acid (PAA), a carboxylic acid or its salt, asulfuric ester or its salt, a sulfonic acid or its salt, a phosphoricacid or its salt, and a sulfosuccinic acid or its salt. The cationicsurfactant used in the aqueous slurry may comprise any one or a mixtureof a primary amine or its salt, a secondary amine or its salt, atertiary amine or its salt, and a quaternary amine or its salt.Optionally, the aqueous slurry may be provided with a copper corrosioninhibitor which may comprise any one or a mixture of heterocyclicorganic compounds including benzotriazole (BTA), triazole, andbenzimidazole. Further, the slurry may contain any combination of thesesurfactants and corrosion inhibitors.

A preferred anionic surfactant is polyacrylic acid (PAA). A preferredcationic surfactant is cetyl pyridinium chloride (CPC). A preferredcopper corrosion inhibitor is benzotriazole (BTA). The addition of PAAimproved slurry dispersability and surface quality. It is believed thatthe addition of PAA modifies the surface charge of the molybdenum oxideparticles such that interaction between the molybdenum oxide particlesand copper is favorable, leading to an increase in the polish rate.Polyacrylic acid (PAA) surfactant may be present in amounts ranging fromabout 0.1 to about 4 wt. % PAA, such as about 0.5 to about 1 wt. % PAA,and more preferably in an amount of about 1 wt. % PAA. The cationicsurfactant cetyl pyridinium chloride (CPC) may be present in amountsranging from about 0.01 to about 1 wt. % CPC, such as about 0.05 toabout 0.5 wt. % CPC, and more preferably in an amount of about 0.1 wt. %CPC. Benzotriazole (BTA) copper corrosion inhibitor may be present inconcentrations ranging from about 0.5 to about 10 milli-molar (mM) BTA,such as about 1 to about 5 mM BTA, and more preferably in aconcentration of about 1 mM BTA.

Embodiments of slurries according to the present invention may also beprovided with amounts of molybdenum sulfide (MoS₂) as a lubricant. Ithas been found that the addition of molybdenum sulfide particlesincreases the polish rate of copper for slurries containing KIO₃ andPAA. Molybdenum sulfide particles may have mean diameters in the rangeof about 0.01 to about 1 micron. Molybdenum sulfide particles may bepresent in amounts ranging from about 0.1 to about 10 wt. % MoS₂, suchas about 0.5 to about 5 wt. % MoS₂, and more preferably in an amount ofabout 1 wt. % MoS₂. Molybdenum sulfide particles having the size rangesherein are commercially available from the Climax Molybdenum Company ofFt. Madison, Iowa (US).

The pH of embodiments of slurries according to the present invention maybe in the range of about 1 to about 14, such as a pH in the range ofabout 3 to about 7, and preferably having a pH of 4. The pH ofembodiments of slurries according to the present invention may beadjusted by the addition of suitable acids (e.g., hydrochloric acid(HCl)) or bases (e.g., potassium hydroxide (KOH)), as would be known bypersons having ordinary skill in the art.

Yet additional embodiments of planarizing slurries according to theinvention may also be provided with supplemental ceramic/metal oxideparticles. Such supplemental ceramic/metal oxide particles used in theaqueous slurry may comprise any one or a mixture of silica, ceria,aluminia, zirconia, titania, magnesia, iron oxide, tin oxide, andgermania.

Embodiments of slurries according to the present invention exhibit highpolish rates for copper when used in the CMP process. More particularly,when potassium iodate (KIO₃) was used as an oxidizing agent in themolybdenum oxide slurries very high copper disk and copper film polishrates (e.g., up to ˜1000 and 470 nm/min, respectively, were obtained, asdetailed in the following examples. Addition of PAA enhanced the filmpolish rate to about 667 nm/min. Further, when molybdenum sulfideparticles were added to slurries containing KIO₃ and PAA, copper filmpolish rates of about 750 nm/min were obtained.

While polish rates with the KIO₃-based slurries of the present inventionare high for copper, the post-polish surface of the copper tended to becovered with a thick, uneven misty layer with roughness values as highas about 150 nm as measured by a non-contact optical profilometer. Ifthe post-polish surface quality is desired to be higher, the CMPpolishing step may be followed by a buffing step. In one embodiment, thebuffing step involved additionally polishing the copper surface with adilute suspension of H₂O₂, glycine, BTA, and colloidal silica inde-ionized water at a pH of 4. The advantage of using an H₂O₂-basedbuffing step is that H₂O₂ reacts spontaneously with molybdenum oxide,thus removing residual amounts of molybdenum oxide that may remain onthe surface. Very clean and smooth copper surfaces were obtained aftersubsequent buffing, some with roughness values as low as 0.35 nm asmeasured by a non-contact optical profilometer.

Polishing selectivity of one embodiment of a slurry of the presentinvention between Cu, Ta, and silicon oxide (SiO₂) was determined to be235:1:1 for Cu:Ta:SiO₂, as presented in Example 24.

Examples 25 and 26 involve the addition of ethylene diamine tetra aceticacid (EDTA) to test the complexing ability of EDTA with copper ions. Thepolish rates for the two specified slurry compositions are presented inTable 5.

In order to provide further information regarding the invention, thefollowing examples are provided. The examples presented below arerepresentative only and are not intended to limit the invention in anyrespect.

EXAMPLES 1-15

Slurries of examples 1-15 were used to polish a copper disk having adiameter of 1.25 inches. The CMP polisher was a Struers DAP® with anIC-1400, k-groove polishing pad. The carrier remained stationary (i.e.,was not rotated). The rotation rate of the platen was 90 revolutions perminute (rpm). The down-force placed on the copper disk was 6.3 poundsper square inch (psi). The slurry flow rate was 60 ml/min. The amount ofcopper removed from the surface of the disk by CMP was determined bymeasuring the weight difference of the copper disk both before and afterpolishing, taking into consideration the density of the Cu material, thearea of the disk that was polished, and the polishing time. This wasthen converted into the rate of removal in terms of nm of copper removedper minute.

The slurries of examples 1-10 all contained 3 wt. % molybdenum oxide(MoO₂) in deionized water. The mean particle size of molybdenum oxidefor examples 1-10 was 1 micron (1000 nm). The mean particle size ofmolybdenum oxide for examples 11-15 was 150 nm. Various amounts andtypes of oxidizing agents were added, as identified in Table 1. Example11 contained 1.5 wt. % MoO₂ with 3 wt. % hydroxylamine hydrochloride((NH₂OH)Cl) as an oxidizing agent. Example 12 contained 1.5 wt. % MoO₂with 3 wt. % potassium permanganate (KMnO₄) as the oxidizing agent.Examples 13-15 all contain 3 wt. % KIO₃ with varying amounts of MoO₂, asnoted. The pH of slurries for examples 1-15 was adjusted to 4.0 by theaddition of hydrochloric acid (HCl) or potassium hydroxide (KOH). Theslurry compositions and polishing rates for the copper disk arepresented in Table 1. TABLE 1 Mean Particle Size Polish Rate ExampleSlurry Composition (nm) pH (nm/min) 1   3% MoO₂ + 0.05 M Fe (NO₃)₃ 10004 69 2   3% MoO₂ + 0.1 M Fe (NO₃)₃ 1000 4 88 3   3% MoO₂ + 0.2 M Fe(NO₃)₃ 1000 4 230 4   3% MoO₂ + 0.5% HNO₃ 1000 4 348 5   3% MoO₂ + 1%HNO₃ 1000 4 221 6   3% MoO₂ + 2% HNO₃ 1000 4 353 7   3% MoO₂ + 3% KI1000 4 157 8   3% MoO₂ + 1% KIO₃ 1000 4 123 9   3% MoO₂ + 2% KIO₃ 1000 4345 10   3% MoO₂ + 3% KIO₃ 1000 4 1014 11 1.5% MoO₂ + 3% (NH₂OH) Cl 1504 68 12 1.5% MoO₂ + 3% KMnO₄ 150 4 31 13   1% MoO₂ + 3% KIO₃ 150 4 16914   2% MoO₂ + 3% KIO₃ 150 4 524 15   3% MoO₂ + 3% KIO₃ 150 4 862

EXAMPLES 16-18

Slurries of examples 16-18 were used to polish a copper film depositedon a silicon substrate by sputter deposition. The copper film had adiameter of 6 inches. The CMP polisher was a Westech Model 372 with anIC-1400, k-groove polishing pad. The carrier was rotated at a rate of 40rpm. The platen was rotated at 40 rpm. The down-force placed on thecopper film was 6 pounds per square inch (psi). The slurry flow rate wasset at 200 ml/min.

The amount of copper removed from the surface of the silicon substrateby CMP was determined by measuring the sheet resistance of the Cu filmboth before and after polishing at 17 points spread across the filmutilizing a home-made paper mask and a 4-point probe. Sheet resistancewas measured at the same points on the film before and after polishing.The measured sheet resistances both before and after polishing were thenconverted to respective film thicknesses before and after polishingbased on the resistivity of the Cu material, the current applied, andthe voltage across the 4-point probe. The difference between thestarting and final thicknesses as 17 points were calculated, an averagethickness loss was obtained which was then divided by the polish time togive the polish rate in nm/min.

The slurries all contained 3 wt. % molybdenum oxide (MoO₂) in deionizedwater and with a potassium iodate (KIO₃) oxidizing agent present in anamount of 3 wt. %. The mean particle size of the molybdenum oxide forexamples 16-18 was 1 micron (1000 nm). Example 17 added 1 wt. % PAA tothe slurry. Example 18 added 1 wt. % PAA and 1 wt. % molybdenum sulfide(MoS₂) to the slurry. The pH of the slurries of examples 16-18 wasadjusted to 4.0 by the addition of hydrochloric acid (HCl) or potassiumhydroxide (KOH). The slurry compositions and polishing rates for thecopper film are presented in Table 2. TABLE 2 Mean Particle Size PolishRate Example Slurry Composition (nm) pH (nm/min) 16 3% MoO₂ + 3% KIO₃1000 4 471 17 3% MoO₂ + 3% KIO₃ + 1% 1000 4 667 PAA 18 3% MoO₂ + 3%KIO₃ + 1% 1000 4 750 PAA + 1% MoS₂

EXAMPLES 19-23

Slurries of examples 19-23 were used to polish a copper film depositedon a silicon substrate by sputter deposition. The copper film had adiameter of 6 inches. The CMP polisher was a Westech Model 372 with anIC-1400, k-groove polishing pad. The carrier was rotated at a rate of 75rpm. The platen was also rotated at 75 rpm. The down-force placed on thecopper film was 4 pounds per square inch (psi). The slurry flow rate wasset at 200 ml/min.

The amount of copper removed from the surface of the silicon substrateby CMP was determined by measuring the sheet resistance of the Cu filmboth before and after polishing at 17 points spread across the filmutilizing a home-made paper mask and a 4-point probe. Sheet resistancewas measured at the same points on the film before and after polishing.The measured sheet resistances both before and after polishing were thenconverted to respective film thicknesses before and after polishingbased on the resistivity of the Cu material, the current applied, andthe voltage across the 4-point probe. The difference between thestarting and final thicknesses as 17 points were calculated, an averagethickness loss was obtained which was then divided by the polish time togive the polish rate in nm/mm.

The slurries all contained 3 wt. % molybdenum oxide (MoO₂) in deionizedwater and with a potassium iodate (KIO₃) oxidizing agent present in anamount of 3 wt. %. The mean particle diameter of the molybdenum oxidefor examples 19-23 was 150 nm. Example 20 added 1 mM benzotriazole (BTA)to the slurry. Example 21 added 1 wt. % polyacrylic acid (PAA) to theslurry. Example 22 added 0.1 wt. % cetyl pyridinium chloride (CPC) tothe slurry. Example 23 added 2 wt. % PAA and 1 mM BTA to the slurry. ThepH of the slurries of examples 19-23 was adjusted to 4.0 by the additionof hydrochloric acid (HCl) or potassium hydroxide (KOH). The slurrycompositions and polishing rates for the copper film are presented inTable 3. TABLE 3 Mean Particle Size Polish Rate Example SlurryComposition (nm) pH (nm/min) 19 3% MoO₂ + 3% KIO₃ 150 4 695 20 3% MoO₂ +3% KIO₃ + 1 mM 150 4 471 BTA 21 3% MoO₂ + 3% KIO₃ + 1% 150 4 997 PAA 223% MoO₂ + 3% KIO₃ + 0.1% 150 4 913 CPC 23 3% MoO₂ + 3% KIO₃ + 2% 150 4660 PAA + 1 mM BTA

EXAMPLE 24

Silicon wafers (6 inch diameter) having a 0.3 micron Ta layer depositedby sputter deposition and wafers having a 1 micron SiO₂ layer applied bythermal oxidation were separately polished with a polishing slurry. Theamount of copper and Ta removed was determined using a four-point probe,and SiO₂ removed from the surface of the silicon wafer by CMP wasmeasured using an optical interferometer, in order to determine the rateof removal in terms of nm of material removed per minute.

The slurry utilized comprised 3 wt % molybdenum oxide (MoO₂) indeionized water with potassium iodate (KIO₃) oxidizing agent present inan amount of 3 wt. %. The mean particle size of the molybdenum oxide forexample 24 was 1 micron (1000 nm). The CMP polisher was a Westech Model372 with an IC-1400, k-groove polishing pad. The carrier was rotated ata rate of 40 rpm. The platen was also rotated at 40 rpm. The down-forceplaced on the copper film was 6 pounds per square inch (psi). The slurryflow rate was 200 ml/min. The slurry composition and polishing rates forCu, Ta, and SiO₂ are presented in Table 4. TABLE 4 SiO₂ Cu Polish TaPolish Polish Slurry Rate Rate Rate Example Composition (nm/min)(nm/min) (nm/min) 24 3% MoO₂ + 3% KIO₃ 471 2 2

EXAMPLES 25 and 26

Slurries of examples 25 and 26 were used to polish a copper disk havinga diameter of 1.25 inches. The CMP polisher was a Struers DAP® with anIC-1400, k-groove polishing pad. The carrier remained stationary (i.e.,was not rotated). The rotation rate of the platen was 90 revolutions perminute (rpm). The down-force placed on the copper disk was 6.3 poundsper square inch (psi). The slurry flow rate was 60 ml/min. The amount ofcopper removed from the surface of the disk by CMP was determined bymeasuring the weight difference of the copper disk both before and afterpolishing, taking into consideration the density of the Cu material, thearea of the disk that was polished, and the polishing time. This wasthen converted into the rate of removal in terms of nm of copper removedper minute.

The slurries of examples 25 and 26 all contained 3 wt. % molybdenumoxide (MoO₂) in deionized water. The mean particle size of molybdenumoxide for both examples 25 and 26 was 1 micron (1000 nm). Variousamounts and types of oxidizing agents were added, as identified in Table5. Slurries of both examples included the addition of 1 wt. % ethylenediamine tetra acetic acid (EDTA) to test the complexing ability of EDTAwith copper ions. The slurry compositions and polishing rates for thecopper disk are presented in Table 5. TABLE 5 Mean Particle Polish SizeRate Example Slurry Composition (nm) pH (nm/min) 25 3% MoO₂ + 3% KI + 1%1000 4 146 EDTA 26 3% MoO₂ + 3% KI + 1% 1000 4 259 KMnO₄ + 1% EDTA

Another embodiment of an aqueous slurry may comprise molybdenum trioxide(MoO₃) and an oxidizing agent. The MoO₃ may be present in an amount ofabout 0.1 to about 10 wt. %, such as about 0.5 to about 10 wt. %, andmore preferably in an amount of about 0.5 to about 5 wt. %. Themolybdenum trioxide (MoO₃) may be provided in powder form such that themolybdenum trioxide (MoO₃) visibly dissolves or substantially visiblydissolves in the oxidizing agent. The molybdenum trioxide powder mayhave a mean particle size of about 10,000 nm (10 microns) and morepreferably less than about 1,000 nm (1 micron), as measured by a Horibalaser scattering analyzer. Generally speaking molybdenum trioxide (MoO₃)powders having these sizes are visibly dissolved in an aqueous solutionof deionized water and the oxidizing agent. As used herein, the terms“dissolved” and “visibly dissolved,” refer to solutions wherein theparticles of MoO₃ are at least partially, although not necessarilycompletely, dissolved. Stated another way, solutions containingparticles of MoO₃ may appear substantially clear or “visibly dissolved”to the naked eye, even though the particles of MoO₃ may not becompletely dissolved.

An alternative embodiment of an aqueous slurry may comprise molybdicacid. The dissolution of molybdenum trioxide in an aqueous solution ofdeionized water and an oxidizing agent may form molybdic acid. Inaddition, molybdic acid may be formed by dissolving molybdenum metal,molybdenum oxides, or molybdates in an oxidizing medium. The term“molybdic acid” as used herein refers to any compound containingmolybdenum and capable of transferring a hydrogen ion in solution.Embodiments of the aqueous slurry of the present invention utilizingmolybdic acid may comprise the same oxidizing agents, complexing agents,surfactants, corrosion inhibitors, acids or bases, and supplementalceramic/metal oxide particles as are listed below for the molybdenumtrioxide aqueous slurry.

The MoO₃ particles may be produced from a variety ofmolybdenum-containing precursor materials, such as, for example,ammonium molybdates and related compounds, as well as molybdenum oxidesprepared from a variety of processes known in the art, whereinmolybdenum precursors and products can be made into particles of varyingsizes. Molybdenum trioxide particles suitable for use in the presentinvention are commercially available from a wide variety of sources,including the Climax Molybdenum Company of Ft. Madison, Iowa (US).

The oxidizing agent used with molybdenum trioxide (MoO₃) may compriseany one or a mixture of hydrogen peroxide (H₂O₂), ferric nitrate(Fe(NO₃)₃), potassium iodate (KIO₃), nitric acid (HNO₃), potassiumpermanganate (KMnO₄), potassium persulfate (K₂S₂O₈), ammonium persulfate((NH₄)₂S₂O₈), potassium periodate (KIO₄), and hydroxylamine (NH₂OH).Hydrogen peroxide oxidizing agent may be present in concentrationsranging from about 0.5 to about 20 wt % H₂O₂, such as about 1 to about10 wt % H₂O₂, and more preferably in a concentration of about 5 wt %H₂O₂. Ferric nitrate oxidizing agent may be present in concentrationsranging from about 0.05 to about 0.2 molar (M) Fe(NO₃)₃, such as about0.1 to about 0.2 M Fe(NO₃)₃, and more preferably in a concentration ofabout 0.2 M Fe(NO₃)₃. Potassium iodate oxidizing agent may be present inconcentrations ranging from about 1 to about 5 wt % KIO₃, such as about1 to about 3 wt % KIO₃, and more preferably in a concentration of about3 wt % KIO₃. Nitric acid oxidizing agent may be present inconcentrations ranging from about 0.5 to about 2 wt % HNO₃, such asabout 1 to about 2 wt % HNO₃, and more preferably in a concentration ofabout 2 wt % HNO₃. Potassium permanganate oxidizing agent may be presentin concentrations ranging from about 1 to about 5 wt % KMnO₄, such asabout 2 to about 4 wt % KMnO₄, and more preferably in a concentration ofabout 3 wt % KMnO₄. Potassium persulfate oxidizing agent may be presentin concentrations ranging from about 1 to about 5 wt % K₂S₂O₈, such asabout 2 to about 4 wt % K₂S₂O₈, and more preferably in a concentrationof about 3 wt % K₂S₂O₈. Ammonium persulfate oxidizing agent may bepresent in concentrations ranging from about 1 to about 5 wt %(NH₄)₂S₂O₈, such as about 2 to about 4 wt % (NH₄)₂S₂O₈, and morepreferably in a concentration of about 3 wt % (NH₄)₂S₂O₈. Potassiumperiodate oxidizing agent may be present in concentrations ranging fromabout 1 to about 5 wt %—KIO₄, such as about 2 to about 4 wt % KIO₄, andmore preferably in a concentration of about 3 wt % KIO₄. Hydroxylamineoxidizing agent may be present in concentrations ranging from about 1 toabout 5 wt % NH₂OH, such as about 2 to about 4 wt % NH₂OH, and morepreferably in a concentration of about 3 wt % NH₂OH.

Additionally, complexing agents may be used in the molybdenum trioxide(MoO₃) aqueous slurry. Complexing agents may comprise any one or amixture of glycine (C₂H₅NO₂), alanine (C₃H₇NO₂), amino butyric acids(C₄H₉NO₂), ethylene diamine (C₂H₈N₂), ethylene diamine tetra acetic acid(EDTA), ammonia (NH₃), family of mono, di, and tri-carboxylic acids likecitric acid (C₆H₈O₇), phthalic acid (C₆H₄(COOH)₂), oxalic acid (C₂H₂O₄),acetic acid (C₂H₄O₂), and succinic acid (C₄H₆O₄) and family of aminobenzoic acids (C₇H₇NO₂).

Glycine complexing agent may be present in amounts ranging from about0.1 to about 5 wt. % C₂H₅NO₂, such as about 0.1 to about 3 wt. %C₂H₅NO₂, and more preferably in an amount of about 0.5 wt. % C₂H₅NO₂.Alanine complexing agent may be present in amounts ranging from about0.1 to about 5 wt. % C₃H₇NO₂, such as about 0.1 to about 3 wt. %C₃H₇NO₂, and more preferably in an amount of about 0.5 wt. % C₃H₇NO₂.Amino butyric acid complexing agent may be present in amounts rangingfrom about 0.1 to about 5 wt. % C₄H₉NO₂, such as about 0.1 to about 3wt. % C₄H₉NO₂, and more preferably in an amount of about 0.5 wt. %C₄H₉NO₂. Ethylene diamine complexing agent may be present in amountsranging from about 0.1 to about 5 wt. % C₂H₈N₂, such as about 0.1 toabout 3 wt. % C₂H₈N₂, and more preferably in an amount of about 0.5 wt.% C₂H₈N₂. Ethylene diamine tetra acetic acid complexing agent may bepresent in amounts ranging from about 0.1 to about 5 wt. % EDTA, such asabout 0.1 to about 3 wt. % EDTA, and more preferably in an amount ofabout 0.5 wt. % EDTA. Ammonia complexing agent may be present in amountsranging from about 0.1 to about 5 wt. % NH₃, such as about 0.1 to about3 wt. % NH₃, and more preferably in an amount of about 0.5 wt. % NH₃.Citric acid complexing agent may be present in amounts ranging fromabout 0.1 to about 5 wt. % C₆H₈O₇ such as about 0.1 to about 3 wt. %C₆H₈O₇, and more preferably in an amount of about 0.5 wt. % C₆H₈O₇.Phthalic acid complexing agent may be present in amounts ranging fromabout 0.1 to about 5 wt. % C₆H₄ (COOH)₂ such as about 0.1 to about 3 wt.% C₆H₄(COOH)₂, and more preferably in an amount of about 0.5 wt. % C₆H₄(COOH)₂. Oxalic acid complexing agent may be present in amounts rangingfrom about 0.1 to about 5 wt. % C₂H₂O₄ such as about 0.1 to about 3 wt.% C₂H₂O₄, and more preferably in an amount of about 0.5 wt. % C₂H₂O₄.Acetic acid complexing agent may be present in amounts ranging fromabout 0.1 to about 5 wt. % C₂H₄O₂ such as about 0.1 to about 3 wt. %C₂H₄O₂, and more preferably in an amount of about 0.5 wt. % C₂H₄O₂.Succinic acid complexing agent may be present in amounts ranging fromabout 0.1 to about 5 wt. % C₄H₆O₄ such as about 0.1 to about 3 wt. %C₄H₆O₄, and more preferably in an amount of about 0.5 wt. % C₄H₆O₄.Amino benzoic acids as a complexing agent may be present in amountsranging from about 0.1 to about 5 wt. % C₇H₇NO₂ such as about 0.1 toabout 3 wt. % C₇H₇NO₂, and more preferably in an amount of about 0.5 wt.% C₇H₇NO₂.

Embodiments of slurries containing molybdenum trioxide (MoO₃) may alsobe provided with a nonionic surfactant, an anionic surfactant, or acationic surfactant. The anionic surfactant used in the aqueous slurrymay comprise any one or a mixture of polyacrylic acid (PAA), acarboxylic acid or its salt, a sulfuric ester or its salt, a sulfonicacid or its salt, a phosphoric acid or its salt, and a sulfosuccinicacid or its salt. The cationic surfactant used in the aqueous slurry maycomprise any one or a mixture of a primary amine or its salt, asecondary amine or its salt, a tertiary amine or its salt, and aquaternary amine or its salt. The nonionic surfactant may be one or amixture of one of the family of polyethylene glycols.

Optionally, the molybdenum trioxide (MoO₃) aqueous slurry may also beprovided with a copper corrosion inhibitor which may comprise any one ora mixture of heterocyclic organic compounds including benzotriazole(BTA), benzimidazole, poly triazole, phenyl triazole, thion and theirderivatives. Further, the slurry may contain any combination of thesesurfactants and corrosion inhibitors.

A preferred anionic surfactant used in the MoO₃ slurry is a salt ofdodecyl benzene sulfonic acid. The addition of a small amount of thedodecyl benzene sulfonic acid (DBSA) anionic surfactant to the slurrydrastically reduced copper coupon dissolution rates to about 0 nm/minuteand blanket copper wafer polish rates of about 750 nm/minute wereobtained. See Example 34. This low copper coupon dissolution rateindicates low dishing of copper lines during pattern wafer polishing.Dodecyl benzene sulfonic acid surfactant and salts thereof (DBSA) may bepresent in amounts ranging from about 0.00001 to about 1 wt. % (DBSA),such as about 0.0001 to about 0.5 wt. % (DBSA), and more preferably inan amount of about 0.001 wt. % (DBSA).

A preferred copper corrosion inhibitor used in the MoO₃ slurry isbenzotriazole (BTA). The addition of BTA to the slurry brought down thedissolution rates drastically, to less than 50 nm/minute. See Examples30-33. Benzotriazole (BTA) copper corrosion inhibitor may be present inconcentrations ranging from about 1 to about 20 milli-molar (mM) BTA,such as about 1 to about 10 mM BTA, and more preferably in aconcentration of about 10 mM BTA.

The pH of embodiments of MoO₃ slurries according to the presentinvention may be in the range of about 1 to about 14, such as a pH inthe range of about 1 to about 5, and preferably having a pH of about2.6. The pH of embodiments of slurries according to the presentinvention may be adjusted by the addition of suitable acids (e.g.,acetic acid) or bases (e.g., potassium hydroxide), as would be known bypersons having ordinary skill in the art.

Yet additional embodiments of MoO₃ polishing slurries according to theinvention may also be provided with supplemental ceramic/metal oxideparticles. Such supplemental ceramic/metal oxide particles used in theaqueous slurry may comprise any one or a mixture of silica, ceria,zirconia, titania, magnesia, iron oxide, tin oxide, and germania. Apreferred supplemental ceramic/metal oxide used in the MoO₃ slurry iscolloidal silicon dioxide (SiO₂). Colloidal silicon dioxide (SiO₂) mayhave an average particle size of about 20 nm.

Embodiments of MoO₃ slurries according to the present invention exhibithigh polish rates for copper when used in the CMP process. Moreparticularly, when molybdenum trioxide MoO₃ particles were dispersed anddissolved in an aqueous solution containing hydrogen peroxide andglycine and used as a copper CMP slurry, high disk polish rates (e.g.,about 2150 nm/minute) were obtained. However, the copper coupondissolution rates in this slurry were also high (e.g., about 1150nm/minute). See Example 28. These high dissolution and disk polish ratesindicate the active chemical nature of the slurry chemicals. One of thereasons why this slurry exhibits such a high chemical reactivity is dueto the partial dissolution of the molybdenum trioxide MoO₃nano-particles, which form molybdic acid. The copper dissolution rategives an indication of the rate at which copper would be removed inthose regions of the wafer that are not subject to mechanical abrasion.With proper choice of the concentrations of the additives and byinclusion of a corrosion inhibitor, polish rates can be tuned accordingto a user's requirements and dissolution rates can be minimized.

As shown in Examples 29 and 30, blanket copper wafer polishing rates ofone embodiment of an MoO₃ slurry of the present invention weredetermined to be as high as about 1200 nm/minute with post CMP surfaceroughness of about 1 nm. The slurries of Examples 29 and 30 werefiltered to remove particles above 1,000 nm (1 micron) in size and 1.0wt % of 20 nm colloidal SiO₂ abrasives were added.

The post-polish surface of the copper was good with post CMP surfaceroughness values of about 1 nm as measured by a non-contact opticalprofilometer. If higher post-polish surface quality is desired, the CMPpolishing step may be followed by a buffing step. In one embodiment, thebuffing step may involve additionally polishing the copper surface withdeionized water for about five to about fifteen seconds at a pH in therange of about 5 to about 7. The advantage of using a deionized waterrinse buffing step is the removal of reactive chemicals from thewafer-pad interface, which removes residual amounts of molybdenum oxidethat may remain on the surface of the wafer-pad. Clean and smooth coppersurfaces were obtained after subsequent buffing using a deionized waterrinse, some with roughness values as low as about 0.5 to 0.6 nm asmeasured by a non-contact optical profilometer.

With proper adjustment of the concentrations of the chemicals added andwith a deionized water rinse for about five seconds at the end of thewafer polishing, very high polish rates (e.g., about 900 nm/minute) andvery low post CMP roughness (e.g., about 0.5 to 0.6 nm) were obtained.Copper coupon dissolution rate in this slurry was low (e.g., about 40nm/minute). When a small amount of an anionic surfactant, such as sodiumdodecyl benzene sulfonate (SDBS), was added to the MoO₃ polishingslurry, copper coupon dissolution rates became about 0 nm/minute,indicating low dishing of copper lines during pattern wafer polishing,and blanket copper wafer polish rates of about 750 nm/minute wereobtained. See Example 34.

The general methodology for pattern wafer copper polishing is to polishthe bulk copper initially at a high polish rate and then, asplanarization is achieved, the copper polish rate is reduced in order tominimize dishing of copper lines. With proper adjustment of the slurryconstituent composition and process parameters, the slurry of thepresent invention can be tuned for this general methodology of polishingat higher rates and then lower rates.

EXAMPLES 27 and 28

Slurries of examples 27 and 28 were used to polish a copper disk havinga diameter of 32 millimeters (mm). The CMP polisher was a Struers DAP®with an IC-1400, k-groove polishing pad. The carrier remained stationary(i.e., was not rotated). The rotation rate of the platen was 90revolutions per minute (rpm). The down-force placed on the copper diskwas 6.3 pounds per square inch (psi). The slurry flow rate was 60ml/min. The amount of copper removed from the surface of the disk by CMPwas determined by measuring the weight difference of the copper diskboth before and after polishing, taking into consideration the densityof the copper material, the area of the disk that was polished, and thepolishing time. This was then converted into the rate of removal interms of nm of copper removed per minute.

Copper coupon dissolution experiments were performed in a 500 ml. glassbeaker containing 400 ml. of the chemical solution. A copper coupon(i.e. 99.99% pure) of dimensions 25×25×1 mm was used as the experimentalsample. The copper coupon was hand polished with 1500 grit sandpaper,washed with dilute hydrochloric acid (HCl) to remove copper oxides fromthe surface, dried in an air stream, and then weighed. The copper couponwas then immersed in the solution for three minutes while continuouslystirring the solution. After the experiment, the copper coupon waswashed repeatedly with a deionized water rinse, dried in an air stream,and weighed. Weight loss was used to calculate the dissolution rate.

Example 27 contained 1.0 wt. % MoO₃ in deionized (DI) water and Example28 contained 1.0 wt. % MoO₃ in deionized (DI) water with 5.0% H₂O₂ and1.0% glycine as an oxidizing agent and complexing agent, respectively.The natural pH of the Example 27 slurry was about 1.8. The natural pH ofthe Example 28 slurry was about 2.6. The remaining percentages notspecified in the below table for the slurry compositions is thepercentage of deionized water. In Example 27, the MoO₃ comprises 1% ofthe slurry composition and the deionized water comprises the remaining99% of the slurry composition. The slurry compositions, copper coupondissolution rates and polishing rates for the copper disk of Examples 27and 28 are presented in Table 6. TABLE 6 Polish Dissolution Slurry RateRate Example Composition pH (nm/min) (nm/min) 27 1.0% MoO₃ in DI Water1.8 60 20 28 1.0% MoO₃ + 5.0% H₂O₂ + 2.6 2150 1140 1.0% glycine in DIwater

EXAMPLES 29-34

Slurries of examples 29-34 were used to polish a copper film depositedon a silicon substrate by sputter deposition. The copper film had adiameter of 6 inches. The CMP polisher was a Westech Model 372 with anIC-1400, k-groove polishing pad. The carrier was rotated at a rate of 75rpm. The platen was rotated at 75 rpm. The down-force placed on thecopper film was 4 pounds per square inch (psi). The slurry flow rate wasset at 200 ml/min.

The amount of copper removed from the surface of the silicon substrateby CMP was determined by measuring the sheet resistance of the copperfilm both before and after polishing at 17 points spread across the filmutilizing a home-made paper mask and a 4-point probe. Sheet resistancewas measured at the same points on the film before and after polishing.The measured sheet resistances both before and after polishing were thenconverted to respective film thicknesses before and after polishingbased on the resistivity of the copper material, the current applied,and the voltage across the 4-point probe. The difference between thestarting and final thicknesses as 17 points were calculated, an averagethickness loss was obtained which was then divided by the polish time togive the polish rate in nm/min.

Copper coupon dissolution experiments were performed in a 500 ml. glassbeaker containing 400 ml. of the chemical solution. A copper coupon(i.e. 99.99% pure) having dimensions of 25 mm×25 mm×1 mm was used as theexperimental sample. The copper coupon was hand polished with 1500 gritsandpaper, washed with dilute hydrochloric acid (HCl) to remove anycopper oxide from the surface, dried in an air stream, and then weighed.The copper coupon was then immersed in the solution for three minuteswhile continuously stirring the solution. After the experiment, thecopper coupon was washed repeatedly with a deionized (DI) water rinse,dried in an air stream, and weighed. Weight loss was used to calculatethe dissolution rate.

The slurries of Examples 29-34 contained 0.5 wt. % molybdenum trioxide(MoO₃) in deionized water. At the end of the wafer polishing a deionized(DI) water rinse was applied for five seconds. Example 29 contained 0.5%MoO₃+5.0% H₂O₂+1.0% glycine+5 mM BTA−filtered with 100 nm filter+1.0%SiO₂. The natural pH of the Example 29 slurry was about 2.9. Example 30contained 0.5% MoO₃+5.0% H₂O₂+1.0% glycine+10 mM BTA−filtered with 100nm filter+1.0% SiO₂. The natural pH of the Example 30 slurry was about2.9. Example 31 contained 0.5% MoO₃+5% H₂O₂+0.5% glycine+10 mMBTA−filtered with 100 nm filter+0.1% SiO₂. The natural pH of the Example31 slurry was about 2.6. Example 32 contained 0.5% MoO₃+5% H₂O₂+0.5%glycine+10 mM BTA−filtered with 100 nm filter+0.5% SiO₂. The natural pHof the Example 32 slurry was 2.6. Example 33 contained 0.5% MoO₃+5%H₂O₂+0.5% glycine+10 mM BTA−filtered with 100 nm filter+1.0% SiO₂. Thenatural pH of the Example 33 slurry was about 2.6. Example 34 contained0.5% MoO₃+5% H₂O₂+0.5% glycine+10 mM BTA+0.001% SDBS−filtered with 100nm filter+1.0% SiO₂. The natural pH for the slurry of Example 34 wasabout 2.6. The average size of the particles of SiO₂ in the slurries ofExamples 29-34 was about 20 nm. The remaining percentages not specifiedin the below table for the slurry compositions is the percentage ofdeionized water in the slurry. The slurry compositions and polishingrates for the copper wafer along with the copper coupon dissolutionrates for Examples 29-34 are presented in Table 7. TABLE 7 Mean ParticleSize of Polish Dissolution Slurry SiO₂ Rate Rate Example Composition(nm) pH (nm/min) (nm/min) 29 0.5% MoO₃ + 20 2.9 1250 70 5.0% H₂O₂ + 1.0%glycine + 5 mM BTA − filtered 1.0% SiO₂ 30 0.5% MoO₃ + 20 2.9 1225 405.0% H₂O₂ + 1.0% glycine + 10 mM BTA − filtered + 1.0% SiO₂ 31 0.5%MoO₃ + 20 2.6 600 35 5% H₂O₂ + 0.5% glycine + 10 mM BTA − filtered +0.1% SiO₂ 32 0.5% MoO₃ + 20 2.6 775 35 5% H₂O₂ + 0.5% glycine + 10 mMBTA − filtered + 0.5% SiO₂ 33 0.5% MoO₃ + 20 2.6 925 35 5% H₂O₂ + 0.5%glycine + 10 mM BTA − filtered + 1.0% SiO₂ 34 0.5% MoO₃ + 20 2.6 750 05% H₂O₂ + 0.5% glycine + 10 mM BTA + 0.001% SDBS − filtered + 1.0% SiO₂

EXAMPLES 35-37

Slurries of Examples 35-37 were used to polish six inch copper blanketfilms. The CMP polisher was a Westech 372 Wafer Polisher with anIC-1400, k-groove polishing pad. The rotation rate of the carrier was 75revolutions per minute (rpm). The rotation rate of the platen was also75 revolutions per minute (rpm). The down-force placed on the copperblanket film was 4.0 pounds per square inch (psi). The slurry flow ratewas 200 ml/min.

The amount of copper removed from the surface of the silicon substrateby CMP was determined by measuring the sheet resistance of the copperfilm both before and after polishing at 17 points spread across the filmutilizing a home-made paper mask and a 4-point probe. Sheet resistancewas measured at the same points on the film before and after polishing.The measured sheet resistances both before and after polishing were thenconverted to respective film thicknesses before and after polishingbased on the resistivity of the copper material, the current applied,and the voltage across the 4-point probe. The difference between thestarting and final thicknesses as 17 points were calculated, an averagethickness loss was obtained which was then divided by the polish time togive the polish rate in nm/min.

Copper coupon dissolution experiments were performed in a 500 ml. glassbeaker containing 400 ml. of the chemical solution. A copper coupon(i.e. 99.99% pure) having dimensions of 25 mm×25 mm×1 mm was used as theexperimental sample. The copper coupon was hand polished with 1500 gritsandpaper, washed with dilute hydrochloric acid (HCl) to remove copperoxides from the surface, dried in an air stream and weighed. The coppercoupon was then immersed in the solution for three minutes whilecontinuously stirring the solution. After the experiment, the coppercoupon was washed repeatedly with deionized (DI) water, dried in an airstream, and weighed. Weight loss was used to calculate the dissolutionrate.

Example 35 contained 1% MoO₃+5.0% H₂O₂+1.0% glycine+5 mM BTA−filteredwith 100 nm filter+1.0% SiO₂. The natural pH of the Example 35 slurrywas about 2.6. Example 36 contained 1% MoO₃+5.0% H₂O₂+1.0% glycine+10 mMBTA−filtered with 100 nm filter+1.0% SiO₂. The natural pH of the Example36 slurry was about 2.6. Example 37 contained 1% MoO₃+5.0% H₂O₂+1.0%glycine+15 mM BTA−filtered with 100 nm filter+1.0% SiO₂. The natural pHof the Example 37 slurry was about 2.6. The remaining percentages notspecified in the below table for the slurry compositions is thepercentage of deionized water in the slurry. The slurry compositions andpolishing rates for the copper wafer along with the copper coupondissolution rates for Examples 35-37 are presented in Table 8. TABLE 8Mean Particle Size of Polish Dissolution Slurry SiO₂ Rate Rate ExampleComposition (nm) pH (nm/min) (nm/min) 35 1% MoO₃ + 5.0% 20 2.6 1230 55H₂O₂ + 1.0% glycine + 5 mM BTA − filtered + 1.0% SiO₂ 36 1% MoO₃+ 5.0%20 2.6 1120 50 H₂O₂ + 1.0% glycine + 10 mM BTA − filtered + 1.0% SiO₂ 371% MoO₃ + 5.0% 20 2.6 760 35 H₂O₂ + 1.0% glycine + 15 mM BTA −filtered + 1.0% SiO₂

The open circuit potential of a copper coupon in the MoO₃ slurry wasnoble to that of a tantalum coupon indicating that galvanic corrosion ofcopper will not be a problem during pattern wafer polishing which willminimize the dishing of copper lines. The details of the experimentalprocedure in obtaining these results are as follows. EG&G model 273APotentiostat/Galvanostat was used to perform potentiodynamicpolarization experiments. A three-electrode configuration consisting ofa working electrode (Cu/Ta coupon), platinum counter electrode, and asaturated calomel electrode (SCE) as a reference electrode was used. Thethree electrodes are immersed in a 250 ml of the chemical solution andthe potential of the working electrode was scanned from −750 mV to about1000 mV with respect to open circuit potential (OCP) and the resultingcurrent density was monitored using a EG&G Princeton Applied Researchmodel 352 softcorr™ II corrosion software.

The general method for pattern wafer polishing is to polish the bulkcopper initially at a high rate and as planarization is achieved, thecopper is removed at a lower rate in order to minimize dishing of copperlines. With proper adjustment of the MoO₃ slurry constituent compositionand process parameters, the MoO₃ slurry of the present invention may betuned for this general method of polishing at a higher rate and then alower rate. Tantalum dissolution and disk polish rates with the sameMoO₃ slurry were both less than 5 nm/minute. High copper blanket waferremoval rates, high selectivity to tantalum, good post CMP surfacefinish and low abrasive content, leading to a reduced number of post CMPdefects and easier post CMP cleaning, make this slurry an attractivecandidate for the first step of copper CMP process.

Another embodiment of an aqueous slurry may comprise one or more solublesalts of molybdenum dissolved in deionized water and an oxidizing agent.Molybdenum forms salts with valencies of 3, 4, or 6, but the hexavalentsalts are the most stable. Soluble salts of molybdenum may be recoveredfrom primary or secondary sources of molybdenum and may include ammoniummolybdates such as ammonium dimolybdate (NH₄)₂Mo₂O₇ (ADM), ammoniumheptamolybdate (NH₄)₆Mo₇O₂₄ (AHM), and ammonium octamolybdate(NH₄)₄Mo₈O₂₆ (AOM). In addition, molybdate salts of sodium, potassium,iron, and other transition metal elements may be used.

The soluble salt (or salts) of molybdenum may be present in an amount ofabout 0.1 to about 10 wt. %, and more preferably in an amount of about0.5 to about 10 wt. %. The soluble salt of molybdenum may be provided inpowder form such that the soluble salt of molybdenum dissolves in thesolution of deionized water and an oxidizing agent. Generally speaking,soluble salts of molybdenum powders are completely visibly dissolved inan aqueous solution of deionized water and the oxidizing agent. As usedherein, the terms “completely dissolved” and “visibly dissolved,” referto solutions wherein the majority of the particles of soluble salt ofmolybdenum are completely dissolved, and preferably wherein all of theparticles of soluble salt of molybdenum are completely dissolved.

The oxidizing agent used with the soluble salt of molybdenum maycomprise any one or a mixture of the oxidizing agents already describedand present in the amounts specified earlier. Additionally, complexingagents may be used in the soluble salt of molybdenum aqueous slurry.Complexing agents may comprise any one or a mixture of the complexingagents already described and present in the amounts specified above.

Embodiments of slurries containing the soluble salt of molybdenum mayalso be provided with a nonionic surfactant, an anionic surfactant, or acationic surfactant. The anionic surfactant used in the aqueous slurrymay comprise any one or a mixture of polyacrylic acid (PAA), acarboxylic acid or its salt, a sulfuric ester or its salt, a sulfonicacid or its salt, a phosphoric acid or its salt, and a sulfosuccinicacid or its salt. The cationic surfactant used in the aqueous slurry maycomprise any one or a mixture of a primary amine or its salt, asecondary amine or its salt, a tertiary amine or its salt, and aquaternary amine or its salt. The nonionic surfactant may be one or amixture of one of the family of polyethylene glycols.

Optionally, the aqueous slurry comprising the soluble salt of molybdenummay also be provided with a copper corrosion inhibitor which maycomprise any one or a mixture of heterocyclic organic compoundsincluding benzotriazole (BTA), benzimidazole, poly triazole, phenyltriazole, thion and their derivatives. Further, the slurry may containany combination of these surfactants and corrosion inhibitors.

A preferred anionic surfactant used in the soluble salt of molybdenumslurry is a salt of dodecyl benzene sulfonic acid. Dodecyl benzenesulfonic acid surfactant and salts thereof (DBSA) may be present inamounts ranging from about 0.00001 to about 1 wt. % (DBSA), such asabout 0.0001 to about 0.5 wt. % (DBSA), and more preferably in an amountof about 0.001 wt. % (DBSA).

A preferred copper corrosion inhibitor used in the slurry comprising thesoluble salt of molybdenum is benzotriazole (BTA). Benzotriazole (BTA)copper corrosion inhibitor may be present in concentrations ranging fromabout 1 to about 20 milli-molar (mM) BTA, such as about 1 to about 10 mMBTA, and more preferably in a concentration of about 10 mM BTA.

The pH of embodiments of slurries comprising the soluble salt ofmolybdenum according to the present invention may be in the range ofabout 1 to about 14, such as a pH in the range of about 1 to about 7,and preferably having a pH of in the range of about 4 to about 6. The pHof embodiments of slurries according to the present invention may beadjusted by the addition of suitable acids (e.g., acetic acid) or bases(e.g., potassium or ammonium hydroxide), as would be readily recognizedby persons having ordinary skill in the art after having become familiarwith the teachings provided herein.

Yet additional embodiments of polishing slurries comprising the solublesalt of molybdenum according to the invention may also be provided withsupplemental ceramic/metal oxide particles. Such supplementalceramic/metal oxide particles may be added to the aqueous slurry ascolloidal particles or as fumed particles. Such supplementalceramic/metal oxide particles used in the aqueous slurry may compriseany one or a mixture of silica, ceria, zirconia, titania, magnesia, ironoxide, tin oxide, and germania. A preferred supplemental ceramic/metaloxide used in the slurry is colloidal silicon dioxide (SiO₂). Colloidalsilicon dioxide (SiO₂) may have an average particle size of betweenabout 10 nm and about 100 nm, and more preferably of about 20 nm toabout 50 nm.

Polishing slurries comprising the soluble salt of molybdenum may beutilized in a method for polishing copper by chemical-mechanicalplanarization. The method comprises providing an aqueous slurrycomprising dissolved soluble salt of molybdenum and an oxidizing agentand polishing copper with the aqueous slurry using a polishing pad and apressure between the copper and the polishing pad of about 0.5 psi andabout 6.0 psi and more preferably between about 0.5 psi and about 2.0psi.

Embodiments of soluble salt of molybdenum slurries according to thepresent invention exhibit high polish rates for copper when used in theCMP process, even when the CMP process is carried out at very lowpressures (i.e., down forces) between the copper and the polishing pad.CMP processes carried out at high pressures (i.e., down forces) maycause undesirable delamination of lower-k dielectric layers.Accordingly, slurries according to the teachings provided herein allowcopper CMP processes to be carried out at low pressures (i.e., downforces), such as pressures in a range of about 0.5-6.0 psi, and morepreferably as low as 0.5-2.0 psi. Use of such low pressures minimizesthe shear forces that act on the low-k layers of dielectric materialsduring the CMP process. Thus, the slurries described herein aredesirable so that the copper CMP processes can be carried out at highthroughput rates while minimizing defects such as micro-scratches,corrosion, dishing, erosion, as well as enabling high cleanability ofthe polished surface that has been exposed to a variety of chemicals andparticles.

The high disk polish rates obtained from CMP processes carried out atlow pressures (i.e., down forces), such as, for example, pressures inthe range of about 0.5 to about 2.0 psi, indicates the active chemicalnature of the slurry chemicals. With proper choice of the concentrationsof the additives, surfactants, complexing agents, and by inclusion of acorrosion inhibitor and an abrasive, polish rates can be selected or“tuned” as desired or required (e.g., to manage the productivity of thecopper CMP process).

EXAMPLES 38-42

Slurries of examples 38-42 were used to polish a copper disk having adiameter of 6 inches. The CMP polisher was a Struers DAP® with anIC-1400, k-groove polishing pad. The carrier remained stationary (i.e.,was not rotated). The rotation rate of the platen was 90 revolutions perminute (rpm) The pressure (i.e., down-force) placed between the copperdisk and polishing pad was 5 pounds per square inch (psi). The slurryflow rate was 60 ml/min. The amount of copper removed from the surfaceof the disk by CMP was determined by measuring the weight difference ofthe copper disk both before and after polishing, taking intoconsideration the density of the Cu material, the area of the disk thatwas polished, and the polishing time. This was then converted into therate of removal in terms of nm of copper removed per minute.

The slurries of Examples 38-42 are all the same except that the weightpercentage of the oxidizing agent, i.e. hydrogen peroxide (H₂O₂), wasvaried for each example. Examples 38-42 all contained 0.5 wt. % ADM+0.5%glycine+0.5% amino butyric acid, 5 mM BTA+1% SiO₂ particles. Example 38contained 0.125% H₂O₂. Example 39 contained 0.35% H₂O₂. Example 40contained 0.50% H₂O₂. Example 41 contained 0.75% H₂O₂. Example 42contained 1.0% H₂O₂. The remaining percentages of each of the slurrycompositions, which were not specified above, represent the percentageof deionized water. The weight percentage of H₂O₂ and the disk polishingrates for the copper disk of Examples 38-42 are presented in Table 9.TABLE 9 % wt. Polish Rate Example Slurry Composition H₂O₂ (nm/min) 380.5 wt. % ADM + 0.5% 0.125%  478 glycine + 0.5% amino butyric acid, 5 mMBTA + 1% SiO₂ 39 0.5 wt. % ADM + 0.5% 0.35% 1244 glycine + 0.5% aminobutyric acid, 5 mM BTA + 1% SiO₂ 40 0.5 wt. % ADM + 0.5% 0.50% 1177glycine + 0.5% amino butyric acid, 5 mM BTA + 1% SiO₂ 41 0.5 wt. % ACM +0.5% 0.75% 862 glycine + 0.5% amino butyric acid, 5 mM BTA + 1% SiO₂ 420.5 wt. % ADM + 0.5%  1.0% 504 glycine + 0.5% amino butyric acid, 5 mNBTA + 1% SiO₂

EXAMPLE 43

The slurry of Example 43 was used to polish an 8 inch silicon waferhaving a copper layer deposited thereon by electroplating. The CMPpolisher was a Westech 372 Wafer Polisher with an IC-1400, k-groovepolishing pad. The rotation rate of the carrier was 75 revolutions perminute (rpm). The rotation rate of the platen was also 75 revolutionsper minute (rpm). The pressure (i.e., down-force) placed between thecopper and the polishing pad was 2 pounds per square inch (psi). Theslurry flow rate was 200 ml/min. The amount of copper removed from thesurface of the wafer by CMP was determined by measuring the thickness ofthe copper layer on the wafer both before and after polishing and takinginto consideration the polishing time. This was then converted into therate of removal in terms of nm of copper removed per minute.

Examples 43 contained 0.5 wt. % ADM+0.5% glycine+0.5% amino butyricacid, 5 mM BTA+1% SiO₂ particles+0.125% H₂O₂. The remaining percentageof the slurry composition, which are not specified above, represent thepercentage of deionized water. The copper film polishing rate forExample 43 was 1130 nm/min.

Another embodiment of an aqueous slurry may comprise other molybdicacids dissolved in deionized water and an oxidizing agent. Such othermolybdic acids may include, but are not limited to, phosphomolybdic acid(PMA), phosphotungstomolybdic acid and vanadiomolybdic acid, forexample, and are readily commercially available.

The molybdic acid may be present in an amount of about 0.1 to about 10wt. %, and more preferably in an amount of about 0.5 to about 10 wt. %.The molybdic acid may be provided in powder form such that the molybdicacid dissolves in the solution of deionized water and an oxidizingagent. Generally speaking molybdic acids are completely visiblydissolved in an aqueous solution of deionized water and the oxidizingagent.

The oxidizing agent used with the molybdic acid may comprise any one ora mixture of the oxidizing agents already described and present in theamounts described earlier. Additionally, complexing agents may be usedin the molybdic acid aqueous slurry. Complexing agents may comprise anyof the complexing agents and provided in the amounts already describedherein.

The oxidizing agents may oxidize the copper as well as react withmolybdate ions present in the slurry. The new per-molybdate orperoxy-molybdate ions are expected to further oxidize and complex withcopper, thereby providing high polish rates. Similar high polishingaction may also occur by use of tungstates, vanadates, chromates andsimilar transition metal oxide ions or peroxy ions with or without themolybdate ions.

Embodiments of slurries containing the molybdic acid may also beprovided with a nonionic surfactant, an anionic surfactant, or acationic surfactant. The anionic surfactant used in the aqueous slurrymay comprise any one or a mixture of the anionic surfactants describedherein and provided in the amounts previously described. Similarly, thecationic surfactant used in the aqueous slurry may comprise any one or amixture of the cationic surfactants and present in the amounts alreadydescribed. The nonionic surfactant may be one or a mixture of one of thefamily of polyethylene glycols already described.

Optionally, the aqueous slurry comprising the molybdic acid may also beprovided with a copper corrosion inhibitor which may comprise any one ora mixture of heterocyclic organic compounds including benzotriazole(BTA), benzimidazole, poly triazole, phenyl triazole, thion and theirderivatives. Further, the slurry may contain any combination of thesesurfactants and corrosion inhibitors.

A preferred anionic surfactant used in the molybdic acid slurry is asalt of dodecyl benzene sulfonic acid. Dodecyl benzene sulfonic acidsurfactant and salts thereof (DBSA) may be present in amounts rangingfrom about 0.00001 to about 1 wt. % (DBSA), such as about 0.0001 toabout 0.5 wt. % (DBSA), and more preferably in an amount of about 0.001wt. % (DBSA).

A preferred copper corrosion inhibitor used in the slurry comprising themolybdic acid is benzotriazole (BTA). Benzotriazole (BTA) coppercorrosion inhibitor may be present in concentrations ranging from about1 to about 20 milli-molar (mM) BTA, such as about 1 to about 10 mM BTA,and more preferably in a concentration of about 10 mM BTA.

The pH of embodiments of slurries comprising the molybdic acid accordingto the present invention may be in the range of about 1 to about 14,such as a pH in the range of about 1 to about 6, and preferably having apH in the of about 4 to about 6. The pH of embodiments of slurriesaccording to the present invention may be adjusted by the addition ofsuitable acids (e.g., acetic acid) or bases (e.g., potassium or ammoniumhydroxide), as would be known by persons having ordinary skill in theart.

Yet additional embodiments of polishing slurries comprising the molybdicacid according to the invention may also be provided with supplementalceramic/metal oxide particles. Such supplemental ceramic/metal oxideparticles may be added to the aqueous slurry as colloidal particles oras fumed particles. Such supplemental ceramic/metal oxide particles usedin the aqueous slurry may comprise any one or a mixture of silica,ceria, zirconia, titania, magnesia, iron oxide, tin oxide, and germania.A preferred supplemental ceramic/metal oxide used in the slurry iscolloidal silicon dioxide (SiO₂). Colloidal silicon dioxide (SiO₂) mayhave an average particle size of between about 10 nm and about 100 nm,and preferably of about 20 nm to about 50 nm.

Polishing slurries comprising the molybdic acid may be utilized in amethod for polishing copper by chemical-mechanical planarization. Themethod comprises providing an aqueous slurry comprising molybdic aciddissolved in deionized water and an oxidizing agent and polishing copperwith the aqueous slurry using a polishing pad and a pressure between thecopper and the polishing pad of between about 0.5 psi and about 6.0 psiand more preferably between about 0.5 psi and about 2.0 psi.

EXAMPLES 44-49

Slurries of examples 44-49 were used to polish a copper disk having adiameter of 6 inches. The CMP polisher was a Struers DAP® with anIC-1400, k-groove polishing pad. The carrier remained stationary (i.e.,was not rotated). The rotation rate of the platen was 90 revolutions perminute (rpm) The pressure placed between the copper and the polishingpad was about 5 pounds per square inch (psi). The slurry flow rate was60 ml/min. The amount of copper removed from the surface of the disk byCMP was determined by measuring the weight difference of the copper diskboth before and after polishing, taking into consideration the densityof the Cu material, the area of the disk that was polished, and thepolishing time. This was then converted into the rate of removal interms of nm of copper removed per minute.

The slurries of Examples 44-49 are all the same except that the weightpercentage of the oxidizing agent, i.e. hydrogen peroxide (H₂O₂), wasvaried for each Example. Examples 44-49 all contained 1 wt. %phosphomolybdic acid (PMA)+10 mM BTA+1% glycine, 1% amino butyricacid+1% SiO₂ particles. Example 44 contained 0% H₂O₂. Example 45contained 0.25% H₂O₂. Example 46 contained 0.50% H₂O₂. Example 47contained 0.75% H₂O₂. Example 48 contained 1.0% H₂O₂. Example 49contained 2.0% H₂O₂. The remaining percentages of each of the slurrycompositions, which were not specified above, represent the percentageof deionized water. The weight percentage of H₂O₂ and the disk polishingrates for the copper disk of Examples 44-49 are presented in Table 10.TABLE 10 % wt. Polish Rate Example Slurry Composition H₂O₂ 44 10 wt. %PMA + 1 mM BTA + 1%   0% 698 glycine + 1% amino butyric acid + 1% SiO₂45 10 wt. % PMA + 1 mM BTA + 1% 0.25% 1670 glycine + 1% amino butyricacid + 1% SiO₂ 46 10 wt. % PMA + 1 mM BTA + 1% 0.50% 4424 glycine + 1%amino butyric acid + 1% SiO₂ 47 10 wt. % PMA + 1 mM BTA + 1% 0.75% 9233glycine + 1% amino butyric acid + 1% SiO₂ 48 10 wt. % PMA + 1 mM BTA +1% 1.00% 13978 glycine + 1% amino butyric acid + 1% SiO₂ 49 10 wt. %PMA + 1 mM BTA + 1% 2.00% 11087 glycine + 1% amino butyric acid + 1%SiO₂

Yet another embodiment of an aqueous slurry may comprise molybdenumtrioxide (MoO₃) dissolved in deionized water and an oxidizing agent. Tothis mixture is added supplemental ceramic/metal oxide particles asalready described herein, but which may be added as colloidal particlesor as fumed particles. As previously described above with regard to themolybdenum trioxide (MoO₃) slurry, the same oxidizing agents, complexingagents, surfactants, corrosion inhibitors, acids, and bases may be usedin various combinations in accordance with the teachings providedherein.

The MoO₃ may be utilized in a method for polishing copper bychemical-mechanical planarization. The method comprises providing anaqueous slurry comprising dissolved MoO₃ and an oxidizing agent andpolishing copper with the aqueous slurry using a polishing pad and apressure between the copper and the pad of between about 0.5 psi andabout 6.0 psi, and more preferably between about 0.5 psi and about 2.0psi.

Embodiments of MoO₃ slurries according to the present invention exhibithigh polish rates for copper when used in the CMP process, even when theCMP process is carried out at very low pressures. More particularly,when molybdenum trioxide MoO₃ particles were dispersed and completelydissolved in an aqueous solution containing deionized water, hydrogenperoxide, and BTA and used as a copper CMP slurry, high disk polishrates (e.g., about 1200 nm/minute) were obtained with a nominal pressure(e.g., about 0.5 to about 2.0 psi). As mentioned, CMP processes carriedout at high pressures may cause undesirable delamination of lower-kdielectric layers provided on the copper. Accordingly, copper CMP shouldbe carried out at low pressures, such as, for example, pressures in arange of about 0.5-6.0 psi, and more preferably pressures as low as0.5-2.0 psi, to minimize the shear forces that act on the low-k layersof dielectric materials during the CMP process. Thus, the slurriesdescribed herein may be used to advantage in copper CMP processesdescribed herein, allowing the processes to be carried out at highthroughput rates while minimizing defects such as micro-scratches,corrosion, dishing, erosion, as well as enabling high cleanability ofthe polished surface that has been exposed to a variety of chemicals andparticles.

The high disk polish rates obtained from CMP processes described hereincarried out at such minimal pressures (e.g., in a range of about 0.5 toabout 2.0 psi) indicates the active chemical nature of the slurry. Oneof the reasons why this slurry exhibits such a high chemical reactivityis due to the complete dissolution of the molybdenum trioxide particles.With proper choice of the concentrations of the additives and byinclusion of a corrosion inhibitor and an abrasive, polish rates can betuned according to a user's requirements and delamination of the low-kdielectric layers can be minimized.

As shown in Example 54, blanket copper wafer polishing rates of oneembodiment of an MoO₃ slurry of the present invention were determined tobe as high as about 1200 nm/minute. The slurries of Examples 50-54 werefiltered to remove any undissolved particles above 1,000 nm (1 micron)in size and 1.0 wt % of 20 nm colloidal SiO₂ abrasives were added.

The post-polish surface of the copper was good with post CMP surfaceroughness values of about 1 nm as measured by a non-contact opticalprofilometer. If higher post-polish surface quality is desired, the CMPpolishing step may be followed by a buffing step. In one embodiment, thebuffing step may involve additionally polishing the copper surface withdeionized water for about five to about fifteen seconds at a pH in therange of about 5 to about 7. The advantage of using a deionized waterrinse buffing step is the removal of reactive chemicals from thewafer-pad interface, which removes residual amounts of molybdenum oxidethat may remain on the surface of the wafer-pad. Clean and smooth coppersurfaces may be obtained after subsequent buffing using a deionizedwater rinse.

The general methodology for pattern wafer copper polishing is to polishthe bulk copper initially at a high polish rate and then, asplanarization is achieved, the copper polish rate is reduced in order tominimize dishing of copper lines. With proper adjustment of the slurryconstituent composition and process parameters, the slurry of thepresent invention can be tuned for this general methodology of polishingat higher rates and then lower rates.

EXAMPLES 50-54

Slurries of examples 50-54 were used to polish copper deposited on asilicon wafer disk having a diameter of 6 inches. The copper wasdeposited by electroplating. The CMP polisher was a Westech Model 372with an IC-1400, k-groove polishing pad. The carrier was rotated at arate of 75 rpm. The pressure placed on the copper disk was 4 pounds persquare inch (psi). The slurry flow rate was 200 ml/min. The amount ofcopper removed from the surface of the disk by CMP was determined bymeasuring the thickness of the copper film both before and afterpolishing, taking into consideration the polishing time. This was thenconverted into the rate of removal in terms of nm of copper layerremoved per minute.

The slurries of Examples 50-54 are all the same except that the weightpercentage of molybdenum trioxide was varied for each example. Examples50-54 all contained 5% H₂O₂+0.5% glycine+10 mM BTA−filtered+1% SiO2particles. Example 50 contained 0 wt. % MoO₃. Example 51 contained 0.5wt. % MoO₃. Example 52 contained 1.0 wt. % MoO₃. Example 53 contained3.0 wt. % MoO₃. Example 54 contained 5.0 wt. % MoO₃. The remainingpercentages not specified above represent the percentage of deionizedwater. The weight % of molybdenum and polishing rates for the copperdisks of Examples 50-54 are presented in Table 11. TABLE 11 % wt. PolishRate Example Slurry Composition MoO₃ (nm/min) 50 5.0% H₂O₂ + 0.5%glycine + 10 mM   0% 350 BTA + filtered + 1% SiO₂ 51 5.0% H₂O₂ + 0.5%glycine + 10 mM 0.5% 900 BTA + filtered + 1% SiO₂ 52 5.0% H₂O₂ + 0.5%glycine + 10 mM 1.0% 900 BTA + filtered + 1% SiO₂ 53 5.0% H₂O₂ + 0.5%glycine + 10 mM 3.0% 1000 BTA + filtered + 1% SiO₂ 54 5.0% H₂O₂ + 0.5%glycine + 10 mM 5.0% 1200 BTA + filtered + 1% SiO₂

EXAMPLES 55-58

Slurries of examples 55-58 were used to polish a copper film depositedon a silicon substrate wafer having a diameter of 6 inches. The copperfilm was deposited by electroplating. The CMP polisher was a WestechModel 372 with an IC-1400, k-groove polishing pad. The carrier wasrotated at a rate of 75 rpm. The platen was rotated at 75 rpm. Thepressure (i.e., down-force) between the copper and the polishing pad wasabout 4 pounds per square inch (psi). The slurry flow rate was set at200 ml/min. The amount of copper removed from the surface of the disk byCMP was determined by measuring the thickness of the copper film bothbefore and after polishing, taking into consideration the polishingtime. This was then converted into the rate of removal in terms of nm ofcopper removed per minute.

The slurries of Examples 55-58 are all the same except that the type ofabrasive was varied for each Example. Examples 55-58 all contained 0.5wt. % MoO₃+5.0% H₂O₂+1.0% glycine+10 mM BTA. Example 55 contained noabrasives. Example 56 contained colloidal alumina (AlO₂) particles,having a mean particle size of 50 nm, as an abrasive. Example 57contained Aerosol® 200 fumed silica particles as an abrasive. Example 58contained colloidal silica (SiO₂) particles, having a mean particle sizeof 20 nm, as an abrasive. The remaining percentages not specified aboverepresent the percentage of deionized water. The effect of the varioustypes of abrasives on the polish rate of a slurry containing 0.5 wt. %molybdenum trioxide is shown in Table 12. TABLE 12 Abrasive Polish RateExample Slurry Composition (1% wt.) (nm/min) 55 0.5% MoO₃ + 5.0% H₂O₂ +No Abrasive 360 10 mM BTA 56 0.5% MoO₃ + 5.0% H₂O₂ + 50 nm 495 10 mM BTAcolloidal alumina (AlO₂) 57 0.5% MoO₃ + 5.0% H₂O₂ + Aerosil ® 200 495 10mM BTA fumed silica (SiO₂) 58 0.5% MoO₃ + 5.0% H₂O₂ + 20 nm 740 10 mMBTA colloidal silica (SiO₂)

Yet another embodiment of an aqueous slurry may comprise molybdenumdioxide (MoO₂) dissolved in deionized water, an oxidizing agent, aspreviously described above. To this mixture is added supplementalceramic/metal oxide particles as already described herein, but which maybe added as colloidal particles or as fumed particles. As previouslydescribed above with regard to the molybdenum dioxide (MoO₂) slurry, thesame oxidizing agents, complexing agents, surfactants, corrosioninhibitors, acids, and bases may be used in various combinations inaccordance with the teachings provided herein.

The MoO₂ may be utilized in a method for polishing copper bychemical-mechanical planarization. The method comprises providing anaqueous slurry comprising dissolved MoO₂ and an oxidizing agent andpolishing copper with the aqueous slurry using a polishing pad and apressure (i.e., down-force) of between about 0.5 psi and about 6.0 psi,and more preferably between about 0.5 psi and about 2.0 psi.

EXAMPLES 59-62

Slurries of examples 59-62 were used to polish a copper coated siliconwafer having a diameter of 6 inches. The copper was coated on the waferby electroplating. The CMP polisher was a Westech Model 372 with anIC-1400, k-groove polishing pad. The carrier was rotated at a rate of 75rpm. The pressure placed on the copper disk was 4 pounds per square inch(psi). The slurry flow rate was 200 ml/min. The amount of copper removedfrom the surface of the disk by CMP was determined by measuring thethickness of the copper film both before and after polishing, takinginto consideration the polishing time. This was then converted into therate of removal in terms of nm of copper removed per minute.

The slurries of Examples 59-62 show the effect of different abrasives onthe polish rates of copper disks. The pH of Examples 59-62 wasmaintained at approximately 4. Example 59 contained 3 wt % KIO₃. Example60 contained filtrate from a solution comprising 3 wt % MoO₃+3 wt %KIO₃. Example 61 contained filtrate from a solution comprising 3 wt %MoO₃+3 wt % KIO₃+3 wt % silica. Example 62 contained filtrate from asolution comprising 3 wt % MoO₃+3 wt % KIO₃+3 wt % alumina. Theremaining percentages of the slurry composition which were not specifiedrepresent the percentage of deionized water. The weight percentage andtype of abrasives and the disk polishing rates for the copper disks ofExamples 59-62 are presented in Table 13. TABLE 13 Polish Rate ExampleSlurry Composition Abrasive (nm/min) 59 3% KIO₃ none 30 ± 3 60 3% MoO₃ +3% KIO₃ none 268 ± 10 61 3% MoO₃ + 3% KIO₃ 3% wt. 353 ± 15 silica (SiO₂)62 3% MoO₃ + 3% KIO₃ 3% wt. 840 ± 17 alumina (AlO₂)

In conclusion, the claimed product and process collectively represent animportant development in CMP technology. The product and processdiscussed above are novel, distinctive, and highly beneficial from atechnical and utilitarian standpoint. Having herein set forth preferredembodiments of the present invention, it is anticipated that suitablemodifications can be made thereto which will nonetheless remain withinthe scope of the invention. The invention shall therefore only beconstrued in accordance with the following claims:

1. An aqueous slurry for chemical mechanical planarization of a copperlayer on a semiconductor substrate, comprising a soluble salt ofmolybdenum dissolved in deionized water and an oxidizing agent.
 2. Theaqueous slurry of claim 1, wherein said soluble salt of molybdenumcomprises an ammonium molybdate.
 3. The aqueous slurry of claim 2,wherein said ammonium molybdate comprises one or more selected from thegroup consisting of ammonium dimolybdate, ammonium heptamolybdate, andammonium octamolybdate.
 4. The aqueous slurry of claim 1, wherein saidslurry comprises about 0.1% to about 10% by weight of said soluble saltof molybdenum.
 5. The aqueous slurry of claim 1, wherein said oxidizingagent comprises one or more selected from the group consisting ofhydrogen peroxide, ferric nitrate, potassium iodate, nitric acid,potassium permanganate, potassium persulfate, ammonium persulfate,potassium periodate, and hydroxylamine.
 6. A method for planarizingcopper, comprising: providing an aqueous slurry comprising a solublesalt of molybdenum dissolved in deionized water and an oxidizing agent;introducing the aqueous slurry between the copper and a polishing pad;applying a pressure between the polishing pad and the copper, saidpressure being in a range of about 0.5 psi to about 6 psi; and movingthe polishing pad and the copper relative to one another.
 7. The methodof claim 6, wherein providing an aqueous slurry comprises dissolving anammonium molybdate in deionized water.
 8. The method of claim 7, whereindissolving an ammonium molybdate comprises dissolving in deionized waterone or more compounds selected from the group consisting of ammoniumdimolybdate, ammonium heptamolybdate, and ammonium octamolybdate.
 9. Themethod of claim 6, wherein said pressure is in a range of about 0.5 psiand about 2.0 psi.
 10. The method of claim 6, further comprising rinsingthe copper with deionized water at a pH of about 5 to about 7 for aboutfive to about fifteen seconds.
 11. A method for polishing copper,comprising: providing a high polish rate slurry comprising a solublesalt of molybdenum dissolved in deionized water and an oxidizing agent;polishing copper with the high polish rate slurry; providing a lowpolish rate slurry comprising said soluble salt of molybdenum dissolvedin deionized water, an oxidizing agent, and a corrosion inhibitor; andadditionally polishing the copper with the low polish rate slurry. 12.The method of claim 11, wherein providing a low polish rate slurrycomprises changing an amount of the soluable salt of molybdenum that isdissolved in deionized water.
 13. An aqueous slurry comprising amolybdic acid dissolved in an oxidizing agent.
 14. The aqueous slurry ofclaim 13, wherein said molybdic acid comprises one or more selected fromthe group consisting of: phosphomolybdic acid, phosphotungstomolybdicacid, and vanadiomolybdic acid.
 15. The aqueous slurry of claim 13,wherein said slurry comprises about 0.1% to about 10% by weight of saidmolybdic acid.
 16. The aqueous slurry of claim 13, wherein saidoxidizing agent comprises one or more selected from the group consistingof hydrogen peroxide, ferric nitrate, potassium iodate, nitric acid,potassium permanganate, potassium persulfate, ammonium persulfate,potassium periodate, and hydroxylamine.
 17. A method for polishingcopper, comprising: providing an aqueous slurry comprising molybdic aciddissolved in oxidizing agent; introducing the aqueous slurry between thecopper and a polishing pad; applying a pressure between the polishingpad and the copper, said pressure being in a range of about 0.5 psi toabout 6 psi; and moving the polishing pad and the copper relative to oneanother.
 18. The method of claim 17, wherein said pressure is in a rangeof about 0.5 psi and about 2.0 psi.
 19. The method of claim 17, whereinproviding an aqueous slurry comprises dissolving a phosphomolybdic acid(PMA) in an oxidizing agent.
 20. The method of claim 17, furthercomprising rinsing the copper with de-ionized water at a pH of about 5to about 7 for about five to about fifteen seconds.
 21. A method forpolishing copper, comprising: providing a high polish rate slurrycomprising a molybdic acid dissolved in an oxidizing agent; polishingcopper with the high polish rate slurry; providing a low polish rateslurry comprising said molybdic acid dissolved in an oxidizing agent,and a corrosion inhibitor; and additionally polishing the copper withthe low polish rate slurry.
 22. A method for polishing copper,comprising: providing an aqueous slurry comprising dissolved MoO₃ and anoxidizing agent; introducing the aqueous slurry between the copper and apolishing pad; applying a pressure between the polishing pad and thecopper, said pressure being in a range of about 0.5 psi and about 6.0psi; and moving the polishing pad and the copper relative to oneanother.
 23. The method of claim 22, wherein said pressure is in a rangeof about 0.5 psi and about 2.0 psi.
 24. A method for polishing copper,comprising: providing an aqueous slurry comprising dissolved MoO₂ and anoxidizing agent; introducing the aqueous slurry between the copper and apolishing pad; applying a pressure between the polishing pad and thecopper, said pressure being in a range of about 0.5 psi and about 6.0psi; and moving the polishing pad and the copper relative to oneanother.
 25. The method of claim 24, wherein said pressure is in a rangeof about 0.5 psi and about 2.0 psi.